Polyphase watt-hour meter construction



Sept. 6, 1938. u z 2,129,010

Patented Sept. 6, 1938 UNITED STATES POLYPHASE WATT-HOUR METER CON-STRUCTION Fred Kurz, Springfield,

Ill., assignor to Sangamo Electric Company, Springfield, 111., acorporation of Illinois Application April 12, 1937, Serial No. 136,337

6 Claims.

My invention relates, generally, to electric measuring devices, and ithas particular relation to polyphase watthour meters.

It has been customary to construct alternating current polyphasewatthour meters with a plurality of discs mounted on a common shaft andeach disc having a watthour meter unit individual thereto for applying adriving torque. The resultant torque that is applied to the common shaftconnecting the discs is equal to the sum of the torques individuallyapplied by the watthour meter units. By this means it is possible todrive a register which will indicate the total energy that has beenconsumed in the circuits in which the watthour meter units areconnected. Since these watthour meter units cooperate with individualdiscs, and, further, since they may be so mounted that there will besubstantially no magnetic interaction therebetween, the torque that isapplied to the shaft is the result solely of the torques individuallyapplied by the several discs, and there is no additional torque appliedby interaction between the various watthour meter units.

It has also been customary to construct polyphase watthour meters formeasuring alternating current in Which a plurality of watthour meterunits are arranged to cooperate with a single disc. It is intended thateach of the units shall apply a torque to the disc which shall be afunction of the power flowing in the circuit to which it is connected.

Because of the relatively close proximity of the watthour meter units inthe single disc type 35 of watthour meter and the fact that they bothcooperate with the same disc, errors in registration may result whichmight not be present when the two disc type of construction is employed.

These errors in registration are caused by the 40 reaction between thewatthour meter units and the disc in such manner that the net torqueapplied to drive it is proportional not only to the sum of theindividual torques caused by each watthour meter unit, but it also isproportional to some function involving the product of the individualtorques.

Therefore, the principal object of my invention is to apply torque to asingle disc of a watthour meter by a plurality of watthour meter unitsin such manner that the torque shall be proportional solely to the sumof the independent torques generated by each unit.

An important object of my invention is to neutralize the reactionbetween the stray magnetic fluxes of each of two watthour meter unitsacting on a single disc and the eddy currents generated therein by theother unit, so that the resultant torque applied to the disc will besubstantially the sum of the torques generated by each unit.

An object of my invention is to provide a high permeability magneticbridge between the cores of a pair of watthour meter units acting on asingle disc to neutralize the stray magnetic fluxes generated by eachunit in such manner that they do not react with the eddy currentsgenerated in the disc by the other unit.

Other objects of my invention will in part be obvious and in part appearhereinafter.

Accordingly, my invention is disclosed in the embodiment hereof shown inthe accompanying drawings, and it comprises the features ofconstruction, combination of elements and arrangement of parts that willbe exemplified in the following detailed description and the scope ofthe application of which will be indicated in the appended claims.'

Fora more complete understanding of the nature and scope of myinvention, reference may be had to the following detailed descriptiontaken in connection with the accompanying drawings, in which:

Figure 1 illustrates, diagrammatically, the construction and connectionsof a single phase alternating current watthour meter;

Figure 2 illustrates, diagrammatically, the eddy currents that aregenerated in the disc by the voltage element of the single phasewatthour meter unit;

Figure 3 illustrates, diagrammatically, the eddy currents that aregenerated in the disc by the current element of a single phase watthourmeter unit;

Figure 4 illustrates, diagrammatically, the arrangement of. two watthourmeter units arranged to drive a single disc;

Figure 5 is aview diagrammatically illustrating how 'my invention may beapplied to the construction shown in Figure 4 for reducing interactionbetween the two watthour meter units;

Figure 6 is a view, in front elevation, of a two unit watthour meterembodying the features of my invention, the cover and register havingbeen omitted in order to more clearly illustrate the invention; and

Figure 7 is a perspective View of the magnetic bridging member that isemployed in practicing my invention.

In order to more clearly demonstrate the novel fe tures of my inventionand to point out the features which I believe underlie it, referencewill first be had to the functioning of a single phase watthour meter inwhich a single watthour meter unit cooperates with a disc to applytorque thereto for measuring the energy that has flowed in a circuit.Referring now particularly to Figure 1 of the drawings, it will beobserved that the reference character I designates an alternatingcurrent circuit, the fiow of energy in which is to be measured by awatthour meter that is shown generally at H. The meter central leg ofwhich is positioned a voltage coil I3 that is connected across theconductors I6. Underneath the core I2 is a C-shaped core I4 that is alsoformed of laminations of magnetic material, and it has wound on its legsa pair of current coils I5 through which the current in the conductorsIEl flows. In the air gapformed between the pole tips I2a, I21) and I20of the core I2 and the pole tips. Ma and [4b ofthe core I4, a disc I6 isrotatably mounted and is arranged to have appliedthereto a torque thatis dependent upon the power in the circuit represented by the conductorsI0, as will be readily understood. A permanent magnet I! is provided fordamping the movement of the disc I6 in the usual manner.

In Figure 2 of the drawings I have illustrated by the curved lines 20and the arrow heads thereon the direction of fiow of eddy currents inthe disc I6 as caused by the fiux flowing between the pole tips IZa,I21; and I20 that is generated by the voltage winding I3. The eddycurrents in the disc I6 underneath. the pole tips'IZa, I217 and I20react with the flux generated by the current winding I5, in accordancewith Lenz law, to produce the necessary torque for rotating the disc I6.3

The eddy currents that are generated in the disc I6 by the flux flowingbetween the pole tips I la and Mb are indicated by the curved lines 2|and the arrow heads thereon. These eddy currents underneath the poletips Ida and Mb react with the flux generated by the voltage winding I3for the purpose of also producing torque for rotating the disc I6.

It will'be observed that the eddy currents represented by the lines 20and 2I in Figures 2 and 3 are not confined to the region underneath thepole tips of thecores I2 and I4 but, rather, that they spread to theremote regions of the disc I6. It will also be observed that thedirections of flow of the eddy currents are not circumferential, butthatthese directions may be resolved into radial and tangentialcomponents. In these same regions remote from the cores I2 and I4, theresimultaneously exist stray magnetic fields that are generated by thevoltage and current windings I3 and I5. These stray magnetic fields maybe separated into components that are either perpendicular, tangential,or radial with respect to the axis of rotation of the disc I6. actionbetween the perpendicular components of these magnetic fields and theradial components of the eddy currents gives rise to forces that tend toproduce rotation of the disc I6. In a watthour meter in which a singleunit is employed and reacts with a single disc, these forces go to makeup the meter characteristics, and they can be readily deter-mined forany particular set of conditions. However, when two or more watthourmeter units are arranged to drive the disc I6, other factors areinvolved which cannot so readily be determined.

II comprises an" E-shaped core formed of, laminations, on the The re- InFigure 4 of the drawings I have illustrated diagrammatically thearrangement of two watthour meter units II and Na for applying torque toa single disc I6, Under any assumed value and phase of current andvoltage applied to the unit II, the torque that is produced by this unitis to some extent influenced by the presence of the unit 'I la which maybe assumed to be excited in some arbitrary manner or to be energizedfrom another phase of a polyphase circuit. This effect is caused bycertain components of the magnetic fields from these units thatinteractwith radial components of the eddy currents generated by the unit II. Asimilar relation existswith respect to the torque that is produced bythe unit IIa. Thus each of the units II and Ila produces both eddycurrents and magnetic fields in remote portions of the disc therefrom,and these various fields and eddy currents may interact to producetorque that is effective to change the registration of the meter as awhole in a rather complex manner. Stated differently, the resultanttorque of the meter under these conditions is equal not only to the sumof the individual torques caused by each of the units II and Ila, but isalso equal to this sum plus some function involving the product of thesetwo torques. In the desired type of meter, the construction is such thatthe torque applied to the disc I6 will be the result only of the sum ofthe two torques generated by the units II and Na, and it is independentof a third term that involves a function of the product of these twotorques.

This desired result is obtained when the meter is so constructed thateach of the watthour meter units reacts only with a single disc, asdescribed hereinbefore. In such a construction the discs are suitablymechanically coupled together, as by being mounted on a common shaft,but the units themselves are completely shielded from each otherelectromagnetically. Moreover, this construction is provided only at theexpense of size and weight, as well as cost.

When the two units are arranged to apply torque to a singledisc--forexample the disc I6,there is a considerable reduction in sizeand weight of the meter, and the cost is likewise reduced. However,provision must be made for compensating for the torque that is appliedto the disc I6 because of the interaction between the two watthour meterunits II and Ila, for example. This compensation takes the form of theprovision of means for reducing the vertical component of the straymagnetic fields in the remote regions of the disc I6where they mayinteract with radial components of the eddy currents of the other unit.

The reduction of the vertical components of the stray fields in theremote regions of the disc I6 is effected by means of an invertedU-shaped bridging member 25 that is shown diagrammatically in Figure 5of the drawings. As there illustrated, the bridging member 25 isprovided with out-turned end portions 25a and 25b that are disposedadjacent the voltage units of the watttil formed of non-magneticmaterial, such as aluminum or an aluminum alloy. The disc I6 isrotatably mounted on the frame member 21 on a shaft 28 that is providedwith a threaded portion 29 for driving a register (not shown) that ismounted on suitable ears or bosses 30 that may be integrally formed withthe frame member 21. The bridging member 25 is secured in position ontop of the frame member 21 by any suitable means, such as the screws 3|that project through clearance holes 32 in the flat common portionbetween the vertical branches of the U-shaped bridging member 25, asshown in Figure '7. An enlarged clearance hole 33 is also provided inthis portion to permit adjustment of the upper bearing of the shaft 28.

In this construction, two permanent magnets H are mounted on the framemember 21 and serve to damp the rotation of the disc l6.

It will be observed that the watthour meter units II and Ila are mountedon opposite sides of the frame member 21, and in this position they arediametrically disposed on opposite sides of the disc lb. The cores l2and M of the element H, and [2d and I40 of the element Ha are positionedat right angles to the disc l6. These cores are excited, respectively,by voltage and current windings l3 and I5 and Na and 15a. The verticalbranches of the inverted U-shaped bridging member 25 are disposedparallel to the cores l2 and l2d, as shown, while the lower outturnedends 25a and 25b extend toward them adjacent the upper surface of thedisc l6. The bridging member 25 is formed preferably of highpermeability material in order to provide the desired neutralizingefiect. Its width throughout its entire length is sufficient to preventthe vertical components of the stray magnetic field of either of theunits II or Ila from reacting with local radial components of eddycurrents from the other unit and producing an undesired torque in thedisc 16. In effect, the bridging member 25 serves to guide the strayfields from one unit to the other over such a path that they do notreact with eddy currents generated in the disc by the other unit, and,as a result, no additional rotational torque in the disc 16 is present.

While the principles underlying the operation of my invention, ashereinbefore outlined may not be correct in their entirety, I wish topoint out that the bridging member 25 constructed and applied as hereindisclosed is efiective to reduce to a minimum, if not to altogethereliminate, any interaction between the two watthour meter units H andIla that are arranged to apply torque to a single disc l6. Since certainchanges may be made in the foregoing construction and differentembodiments of the invention may be made without departing from thescope thereof, it is understood that the construction shown in theaccompanying drawings and described hereinbefore shall be interpreted asillustrative and not in a limiting sense.

I claim as my invention:

1. In a polyphase induction watthour meter, in combination, a rotatabledisc, a plurality of induction watthour meter units cooperating withsaid disc for applying torque thereto, and means magnetically bridgingbetween said units in such manner that the torque applied to said discby the interaction of said units is substantially reduced.

2. In a polyphase induction watthour meter, in combination, a rotatabledisc, a pair of induction watthour meter units mounted on opposite sidesof said disc for applying torque thereto, and a magnetic bridge memberdisposed between the cores of said units whereby the torque applied tosaid disc by interaction of said units is substantially reduced.

3. In a polyphase induction watthour meter, in combination, a rotatabledisc, a pair of induction watthour meter units mounted on opposite sidesof said disc for applying torque thereto, and a bridge member formed ofhigh permeability metal disposed between the cores of said elements insuch manner as to reduce the effects of the components of stray magneticflux of each unit at right angles to said disc in reacting with eddycurrents generated in said disc by the other unit whereby the torqueapplied to said disc is substantially the result of said units actingindividually.

4. In a polyphase induction watthour meter, in combination, a rotatabledisc, a pair of induction watthour meter units, non-magnetic frame meansmounting said units on opposite sides of said disc for applying torquethereto, and a magnetic bridge member carried by said non-magnetic framemeans with its ends adjacent said disc and the cores of said units forneutralizing the reactions between the magnetic flux of each unit andthe eddy currents generated in said disc by the other unit.

5. In a polyphase induction watthour meter, in combination, a rotatabledisc; a pair of induction watthour meter units mounted on opposite sidesof said disc for applying torque thereto, each of said units includingvoltage and current elements having magnetic cores disposed at rightangles to said disc; and an. inverted U-shaped magnetic bridge membermounted between said voltage elements with the branches thereof beingdisposed substantially parallel to the cores of said voltage elementsand the ends thereof being disposed in proximity to said disc forneutralizing the reactions between the stray magnetic flux of each unitand the eddy currents generated in said disc by the other unit wherebythe torque applied to said disc is substantially the result of saidunits acting individually.

6. In a polyphase induction watthour meter, in combination, anon-magnetic frame, a disc rotatab-ly mounted on said frame; a pair ofinduction watthour meter units carried by said frame on opposite sidesof said disc for applying torque thereto, each of said units includingvoltage and current elements having magnetic cores disposed at rightangles to said disc; and an inverted U-shaped bridge member formed ofhigh permeability metal carried by said frame between said units withthe branches thereof being disposed substantially parallel to the coresof said voltage elements and the ends thereof being disposed inproximity to said disc and turned outwardly toward said cores wherebythe torque applied to said disc is substantially the result of saidunits acting individually.

FRED KURZ.

